In the past most trenching excavation was accomplished by the use of trenching machines; however, since the advent of the Federal Occupational Health and Safety Act and its strigent and varying requirements dictating the sides of excavations must be sloped in accordance with the type soil, the trenching machine has become limited in the areas where it may be used. Also, any trenching machine, without extensive modification, is limited to a given size and depth of trench. Muddy terrain and sticky soil conditions prohibit the use of trenching machines in many instances. Therefore, the backhoe with its greater versatility has become the most predominant excavation machine.
The advent of the hydraulic backhoe has opened vast new fields for this machine in all types of construction. Hydraulics enabled designers to build very small to extremely large machines, all very powerful, but compact and manuverable and at comparatively economical prices. Today it seems that everyone moves dirt with backhoes, and most manufacturers of earth moving equipment build backhoes.
A problem that plagues all backhoe users at some time or another, is the dumping or ejecting of material from the bucket when digging in sticky, cohesive material. The hydraulic backhoe provides the means for a comparatively small machine to exert a tremendous force on the bucket. The bucket is constructed long and deep in order to utilize this force. To facilitate easy movement through the cut and to enable the operator to trim the sides of the cut, the bucket is flared in front, that is, the bucket is wider in front than in the back. This feature also speeds the dumping of excavated material.
The asymmetrical, flared design of the bucket is ideal under most conditions and allows a maximum amount of material to be excavated and carried by each cycle of the machine; however, in muddy, sticky conditions it has the opposite effect because the tremendous forces involved compacts the sticky material into the tapered bucket to such a degree that it will not dump out.
This problem accounts for the vast majority of hydraulic and mechanical failures of the machine when digging in muddy and otherwise easy conditions. When this soil condition is encountered and the material does not eject, the operator first attempts to remove the material by shaking the bucket. This is done with the boom fully extended and the bucket in the dump position by moving the control levers rapidly back and forth, thereby creating incalculable pressures and surges in the hydraulic system. These pressures and surges put undue and many times prohibitive stress on the entire hydraulic system, causing failures of hose, valves, pumps, cylinders etc. Rapid movement of the heavy extended load also places great strain and shock on all of the mechanical and structural components of the machine. Failing to eject in this manner, other attempts are made, such as pounding the bucket against the ground, rocks, or other objects. This action not only results in frequent failure to eject the load, but also does expensive damage to the bucket and machine. Extraction of the material by hand using sharpshooters and bars is difficult and time consuming and is usually resorted to only once or twice per day. Normally, under these conditions, the operator will simply continue to dig with a full bucket and the only material excavated is that amount which can be heaped on top of the already packed bucket. This makes the machine work extremely hard and the rate of production is greatly reduced.
In the past there has been a number of attempts to build bucket cleaners, but to date, none appear to have been completely successful. All known approaches to solving this problem have been mechanically actuated with a cleaner bar mounted in and remaining inside the bucket. There are a number of problems associated with this approach and at the present time, results are not satisfactory.
It is therefore desirable to provide an excavating machine which has a bucket cleaning device that can be retracted out of the way of the bucket when it is not in use, and which can be selectively employed whenever sticky material must be ejected from the bucket. It is furthermore desirable that such a device have the capability of being removed from the machine when it is not needed; and furthermore, that provision be made by which the cleaning blade can efficiently follow the irregular contour of the bottom of an ordinary backhoe bucket. Furthermore, it would be desirable to have provided means by which the cleaning blade is automatically extended into contact with the bottom of the bucket, and thereafter automatically retracted away from the bucket.